Boss was one of four Street Crime Unit cops who opened fire on Diallo in February 1999, as he was reaching for his wallet.

They fired 41 shots at Diallo in the mistaken belief he was reaching for a gun. They hit the 22-year-old immigrant from Guinea 19 times, killing him in the vestibule of the building where he lived on Wheeler Avenue in the Bronx.

Diallo's death swiftly became a flashpoint for activists protesting police brutality, both locally here in New York and across the nation.

Now 16 years later, the shooting of Diallo remains a contentious, disturbing chapter in the NYPD'shistory.

Sources close to the NYPD told the Postthat Boss "deserved" the promotion as he passed the sergeant's exam and had no "current investigations."

CBS New York reportedthat while Boss remained in the NYPD, the other three officers involved in Diallo'sdeath all left the force: one retired and two became firefighters.

Boss gained national attention again years after he and the other officers were cleared of criminal charges when he fought, and lost, in court to get his service weapon returned.

Yet, in 2012, then-Commissioner Ray Kelly agreed to the request.

Patrolmen's Benevolent Association headPatrick J. Lynch said in statement, "This police officer was exonerated in a criminal trial and in a thorough departmental review and there was no reason to deny him full restoration."